Seatalk NG with Garmin plotter: ETA and GPSTime?

chewi

chewi

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I spent the weekend on a mates new to him boat and we struggled to get some info from a ~4yr old Garmin GPSmap 520 on his Raymarine ST60/70 instruments on Seatalk nG

Fundamentally the connections are good, eg while navigating we can see the Lat long, SOG etc, goto waypoint name , BTW,DTW etc, on the Raymarins instruments but when configured to show ETA or other waypoint related data.they have no data.


I don't yet know how the garmin is connected (eg via NMEA & a seatalk adapter or via nmea2000 , the wiring is a jumble of tie-wrapped looms). but it is connected somehow to get lat/long and GPS.

Is there some fundamental obstruction here. eg does seatalk ng only support eta from a raymarine plotter?

also:
is there any way to get GPStime down to the second on the Raymarine displays for starting races ? I can only find hh:mm in 24/12 hr format. not hh:mm:ss in any format.

( I know about the raymarine race timers, which seem good for participants , but they don't help the OOD alone on the committeee boat to initiate the race to GPS timing, and the garmin GPSmap has unhelpfully been installed out of sight in the cabin.
 
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Seatalk ng is just N2K with different cables. The PGNs should be standard. Most are quite rigidly defined albeit there are some where an Evil Vendor (TM) could effectively proprietar-ise them, but that's unlikely to be the cause here.

You'll need to trace the messages. Which 0183 sentences/N2K PGNs the Garmin box outputs, what the protocol convertor does with then and which PGNs the Raymarine accepts and displays.

NMEA0183 is easy to read and loadsa info on sentences available with a web search. The PGNs are defined in freely available documents on the NMEA website (www.nmea.org) down to the field level but you need to pay up if you want to go further and get down to the definition at the byte/bit level.
 
thankyou., I have learnt a bit googling all this.

I can't yet confirm the GPSmap model & whether it supports nmea 2000, but I'm now convinced its connected with nmea 0183, so we only see the limited content of the outgoing minimum nav sentence RBM.
I can see that a nmea0183 protocol; converter can connect to nmea2000, but it only maps the limited 0183 fields, it doesn't calculate any of the missing ones.

I think the nmea 2000 nav sentence 12924 feeds the fields the raymarine ST60/70 instruments offer but fail to display with the 0183 connection.
So it seems if I can connect garmin to nmea2000 to seatalkng It would do what we expect.

Looking at the gpsmap 520/521 installation guide the GPSmap 52x has to be 30-38" from the compass!!
With the compass already on the centreline in the middle of the dashboard that limits me to at least 3 feet one side or other of the centre line!!
No wonder it's installed in the cabin.
 
The info I've got on 129284 shows the ETA but doesn't say whether this field is optional.

129284 Navigation Data
Field # Field Description
This parameter group provides essential navigation data for following a route. Transmissions will originate from products that can
create and manage routes using waypoints. This information is intended for navigational repeaters.
1 SID
2 Distance to Destination Waypoint
3 Course/Bearing Ref.
4 Perpendicular Crossed
5 Arrival Circle Entered
6 Calculation Type
7 ETA Time
8 ETA Date
9 Bearing, Origin To Destination Waypoint
10 Bearing, Position To Destination Waypoint
11 Origin Waypoint Number
12 Destination Waypoint Number
13 Destination Wpt Latitude
14 Destination Wpt Longitude

Which convertor are you using? The Actisense documentation (on the off chance it is that one) says it converts RMB to 129283 & 129284 (but 129283 is just XTE really).

129284 can't carry the time so I'd expect 129033 to be produced somehow. Are there any other NMEA0183 sentences being transmitted other than RMB? GLL & GGA perhaps.
 
I don't know yet which converter (if any) is used to connect the 0183, but I have concluded that all it does is filed map nme0183 values to nmea2000 without any clever maths.

Likewise I have yet to confirm if it is a GPSmap521 (inc nmea 2000) or a gpsmap520 (nme0183 only).
I think I have to resolve that to move on.

Timewise I am sure the raymarine instruments are receiving the GPS local time as hhmmss from the GPS whether by GGA;GLL or other GPS sentence as they all seem to send time as hhmmss, but I can find no way to display it on the Raymarine kit in anything other than hh:mm ie without the :ss.
 
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So, to summarise, you're asking for advice but you don't know which plotter it is, you don't know which NMEA protocol it's connected through, you don't know if there's a converter and, if there is, you don't know what type it is. How can anyone give you any sensible advice?
 
I have already had polite and useful advice here thankyou, and it points to what protocol the GPS connects with, rather than anything about the Raymarine instruments.

Thankyou for your help anyway.
 
chewi said:
I don't know yet which converter (if any) is used to connect the 0183, but I have concluded that all it does is filed map nme0183 values to nmea2000 without any clever maths.

Likewise I have yet to confirm if it is a GPSmap521 (inc nmea 2000) or a gpsmap520 (nme0183 only).
I think I have to resolve that to move on.

Timewise I am sure the raymarine instruments are receiving the GPS local time as hhmmss from the GPS whether by GGA;GLL or other GPS sentence as they all seem to send time as hhmmss, but I can find no way to display it on the Raymarine kit in anything other than hh:mm ie without the :ss.
Click to expand...

I wouldn't expect the protocol convertor to create data to fill any gaps. As there's not a 1:1 correspondence between NMEA0183 sentences and NMEA2000 PGNs, so I think it is quite common for them to use data from two input messages to form one output, or to produce multiple outputs from one input. So I guess if there's not the data in the RMB for ETA to be transposed then it must be optional and is missed out.

What are the Raymarine instruments in question? Would they be able to calculate the ETA?

Easy to tell if the Garmin supports N2K and the DeviceNet connector is obvious when you see it. Garmin tend to use plastic fittings but are otherwise as normal DeviceNet. (Bigger than Seatalk ng with screw on connector - a web search should get you pictures.) If you don't have this and are connecting individual wires it is probably 0183.

Sounds like it's an issue of whether the seconds can be displayed rather than the data not getting through.
 
lpdsn said:
I wouldn't expect the protocol convertor to create data to fill any gaps. As there's not a 1:1 correspondence between NMEA0183 sentences and NMEA2000 PGNs, so I think it is quite common for them to use data from two input messages to form one output, or to produce multiple outputs from one input. So I guess if there's not the data in the RMB for ETA to be transposed then it must be optional and is missed out.

What are the Raymarine instruments in question? Would they be able to calculate the ETA?

Easy to tell if the Garmin supports N2K and the DeviceNet connector is obvious when you see it. Garmin tend to use plastic fittings but are otherwise as normal DeviceNet. (Bigger than Seatalk ng with screw on connector - a web search should get you pictures.) If you don't have this and are connecting individual wires it is probably 0183.

Sounds like it's an issue of whether the seconds can be displayed rather than the data not getting through.
Click to expand...

thanks, that about sums up where I am , but without disantling my mates boat I cant find out how its connected, so it will have to wait.

Raymarines are St60 graphic ST70 multifunction, St?? analoguewind and StT60 tridata (speed/depth).

it's the ST70 I'm really looking at.
 
Most Garmin's have a menu page where you can turn on and off which pgn's are transmitted. Take a look at this first IIWY.
 
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